Scientific Chronicle.

RECENT EARTHQUAKES.

FEW of the many accounts of the late Earth movements in Charleston, South Carolina, and in the surrounding States are reliable, or such as to give us any data for a true scientific study of the phenomenon. As earthquakes have occurred only at very far off intervals in most of our States, no wonder that no provision has been made for their exact observation. In fact, even when foreseen, observations on the attendant phenomena are not easily made, as a recent experiment has made apparent. Last October, on the occasion of the blasting of Flood Rock, in Long Island Sound, preparations were made to study the propagation of the earth's wave resulting from that great explosion, which may be compared to a diminutive earthquake. The results, however, were by no means satisfactory. It was to be expected, then, that in the late unforeseen shock of August 31st there would be much uncertainty in determining the centre of oscillation of the earthquake waves and their rate of propagation. Speaking of the Flood Rock explosion in last January's CHRONICLE, we explained how the waves coming from an earth-jar are propagated. At the time, the ultimate causes of the disturbances being known, this was the only problem to be studied. In natural earthquakes the ultimate cause is the first subject of inquiry. As is well known, scientists admit that this cause is either a subterranean explosion, connected with volcanic action, or a sudden bodily movement of large areas of the earth's surface, due probably to the contraction of the inner mass. These movements, when made gradually, do not produce any noticeable disturbance, but if the earth's crust resists the contractions, and the force accumulates, the yielding finally takes place with great crushing and fissures. To these two causes, at different times and on different occasions, the production of earthquakes is attributed; and to the latter, in our opinion, the earthquake at Charleston is due. The first confirmation of this statement may be found in the fact that the shock coincided with a very high tide arising from the combined action of sun and moon on the day of the solar eclipse of August 29th. This tide must have produced a very high pressure all along the coast. Moreover, it is an accepted opinion in geology that there is a line of weakness in the earth's crust, starting from North Carolina and going somewhat in the direction of Toronto. It is not surprising, then, that a force accumulated near Charleston, perhaps for a long time, caused the recent disturbance. Another confirmation may be had from the chemical analysis of some specimens,-for which we are indebted to a friend -taken from the fissures near Charleston. They were found to consist mostly of silicates of sodium, potassium and aluminium, with traces of

iron oxide and calcium phosphate-in other words, of sand and mud; giving, therefore, no sign of volcanic action. We found in them no sulphur, though according to some accounts the presence of sulphur in the air after the shock was perceptible. The same conclusion seems to be indicated by a singular feature connected with the earthquake. The artesian well which supplies the reservoir of Charleston, and which is said to have a depth of over 1500 feet, showed no change of flow or temperature.

The manner of propagation of these earth waves, however incomplete our knowledge of their causes may be, seems to be better known. They moved more rapidly in a direction almost north and south, or in the direction of the line of weakness, than from east to west. They were consequently elliptical with the major axis of the ellipse lying along the direction of the line of weakness. It was furthermore noticed that at different places the intensity of the tremor was different, and that it was wholly unperceived in places situated between districts very badly shaken. This apparent anomaly will find an easy explanation in the geological formation of such places. They are areas of solid formation isolated from others by soft areas incapable, on account of their want of elasticity, of conveying the earth waves. Another phenomenon generally attending earthquakes on the coast, but fortunately absent in this case, is the advance of great sea-waves. Their formation is very easily explained: when the shock comes, the ocean-bottom is lifted up or slips down, and a great mass of water is hurled one way or other with force enough to sweep every obstacle from its path. Its absence in the present instance is, we presume, due to the fact that the earth waves, starting inland, ran towards the ocean; hence if the water wave was formed it would have been noticed only at sea.

At the present date of writing (September 15th), no further scientific remarks on this subject seem to be called for; should some new facts throwing light on the nature of the phenomena be made known, we shall return to the subject. We will merely add that no scientific ground can be assigned for the prediction of another earthquake on September 29th. It is true that about that time the sun and moon will again be in conjunction, and Mars will be in the same portion of the heavens; but this does not prove anything in favor of such a prediction.

MEETING OF THE AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE.

On the 18th of August the American Association for the Advancement of Science met at Buffalo, and continued in session until the 24th, inclusive. We shall give a brief account of the scientific part of the proceedings, after having made some remarks on the nature of the Association itself. The matter treated in the meetings will give us occasion to

touch on the scientific work that has been done during the last few months.

Nature of the Association.-Like the British Association for the Advancement of Science, after which the American is modelled in its general features, this Association proposes, "by periodical and migratory meetings, to promote intercourse between those who are cultivating science in different parts of America, to give a stronger and more general impulse and more systematic direction to scientific research, and to procure for the labors of scientific men increased facilities and a wider usefulness."

The Association, besides a few Patrons,-at present there are only three,—who are classed as such when they give the sum of one thousand dollars or more, is composed of Members and Fellows. The former are elected by the standing committee upon the written recommendations of two members. From among these the same committee elect by ballot the Fellows, or such persons as are by profession engaged in science, or have by their labors aided in its advancement. The number of Fellows is necessarily more limited than that of Members; at present it is about six hundred, while the Members in July of this year numbered nearly two thousand.

The Association is divided into many small societies, or rather sections. Each Section is composed of Members who apply themselves to the same branch of scientific research. According to the present arrangement, the Sections embrace the following studies: Mathematics and Astronomy, Physics, Chemistry, Mechanical Science, Geology and Geography, Biology, Anthropology, Economic Science and Statistics. Each one of the Sections is presided over by a vice-president and has its own secretary, while the whole Association has a president, a general and assistant secretary, besides the permanent secretary, Professor F. W. Putnam, of Cambridge, Mass., and treasurer, W. Lilly, of Mauch Chunk, Pa. All these officers, except the last two, are elected every year by a standing committee comprising the past presidents and officers of both. the preceding and actual meeting.

The Proceedings of each meeting are printed, but it is to be regretted that the distribution of these publications cannot be made earlier. Without them no one can have a thorough knowledge of what has been accomplished in a meeting, for it is not in the general sessions, but in those of the Sections, that the real scientific work is done, and these Sections choose different places for their meetings. Thirty-four volumes of records show how regularly the Association has met in past years, except those between 1861-65. The two most important meetings ever held were that at Boston in 1880, and the one at Philadelphia in 1884. The latter was of special interest, owing to the presence of many members of the British Association, which was convened at Montreal that year. Meeting at Buffalo.-Buffalo is the only city which has been honored by the presence of the Association three times since 1848; the meetings having taken place there at intervals of ten years, in 1866, 1876 and this year. Notwithstanding the many attractions of this great city, its

easy means of access, the interest shown by the local committee and the prestige of its former successful gatherings, the number of members present did not go beyond one-fourth of the whole body. Those, however, who had the good fortune to be there say that the sessions were most enjoyable. About two hundred papers were read, and though they did not show great originality, and contained no important discoveries, nearly all of them were of sufficient interest to command the attendance of not only members of the Association, but of ladies and gentlemen living in Buffalo.

Address of Professor H. A. Newton.-On the morning of the 18th of August, in the first general session, some preliminary business was settled, and in the evening the real work was taken up. It was during the second general session of the day that Professor Newton, the retiring president, gave his address, which by competent men has been declared the most prominent feature of the Buffalo meeting.

Unlike many of his predecessors, and contrary to the custom followed by the presidents of the British Association, Professor Newton, instead of a general subject, took a special one, which has been, perhaps, the most important study of his life-Meteorites, Meteors and Shooting Stars. Were justice done it, we should give the entire paper, or at least a longer account than our space will allow. We shall attempt the following synopsis, which will enable the reader, we think, to form an idea of its merits.

Having stated the facts generally admitted by scientific men about those luminous phenomena, he proves that meteors cannot be produced otherwise than by solid bodies, which, in virtue of their own motion, enter our atmosphere and become luminous by their friction with the air. Contrary to the opinion of some scientists, he holds that the shooting stars, or meteors, which may be noticed any clear night, and the star showers, or luminous displays, which occur at certain times-one of them took place November 27th, 1885-are of the same origin, and that from either meteors or luminous displays come the meteorites we find on the earth's surface. From the study of many specimens, as also by theoretic deductions, he surmises that the average size of meteoric bodies is rather small; and hence he scouts the opinion of Meyer and others who believe that the preservation of the calorific energy of the sun may come from the fall of such bodies into its surface.

Passing to the origin of meteoric matter, Professor Newton holds that it cannot be due to the sun or the earth's volcanic eruptions, nor to the planets proper or the moon, and therefore concludes that it must be of cometary formation. Moreover, he assumes that comets themselves are condensed from nebulous matter, and this matter may come from the outer portions of the original solar nebula, or from nebula distinct. from it.

Papers of the Sections.—We would go beyond the limits of our space were we to attempt a minute analysis of all the papers; moreover, the subject matter of some of them would prove most uninteresting to the general reader. Therefore we propose to select only those that con

tain new results of science. We may mention for the Section of Mathematics and Astronomy the paper of Professor B. A. Gould, of Cambridge, on the "Photographic Determination of Stellar Position." Twice already we have had occasion to mention in our "Chronicle " the great assistance that Photography has of late afforded Astronomy. We have here a new instance of it. Dr. Gould, after briefly recalling the history of celestial photography, states the work he himself did. while he was in charge of the Observatory of Cordova, Argentine Republic. He succeeded in securing nearly fourteen hundred photographic plates of southern star clusters, and he is now engaged in a long work, a reduction of the results, which, no doubt, will increase our knowledge of the southern stars, at present much less known than those of our own hemisphere.

Mr. Chandler's paper on A Comparative Estimate of Methods and Results in Stellar Photometry" was attentively listened to, and called forth great discussion. Mr. Chandler tried to substantiate by a remarkable number of results the unexpected and, to some, startling statement, that the attempts to determine the relative brightness of the stars, made of late by experimental photometry, had all proved failures and had not disclosed a more uniform scale of magnitude than Argelander's, who, by estimates of the naked eye, determined the stellar magnitudes.

Physics. Mr. Mendenhall reported the progress which had been made in the study of atmospheric electricity. He noted also a phenomenon, entirely new to him, which happens in the use of resistance coils. He says when a current passes for some time through such coils, upon short circuiting, a reverse current is found to pass through them. The presence of this last current may doubtless be classed under the general head of polarization, but by simple polarization it would be difficult to account for its continuance there for hours.

To the surprise of many, only two papers on electricity were given in this section, and this certainly was not owing to any lack of matter. Perhaps the following little items may interest and please those of our readers who use the electric light. An eminent oculist, after examining the eyes of one thousand one hundred persons who work by the incandescent electric light, failed to find any injurious effects, while it seems that the arc light, at close range and used for long work, is very apt to injure the eye. From a hygienic point of view, either the incandescent or arc light is better than common gas for lighting large rooms. After elaborate experiments made in a Munich theatre, Dr. Breslauer states that gas-light rendered the air of that hall four times as impure as electric light.

Among the most important papers on chemical subjects was that of Professor C. F. Mabery, of Cleveland, Ohio, on "The Decomposition of Certain Products of the Cowles' Electric Furnaces." At last year's meeting at Ann Arbor he contributed a paper on the "Electrical Furnaces,' an abstract of which may be seen in the records of that date. In the issue of last January we gave an account of the electrical furnace, and in the last number returned to the same subject, alluding to the new